revert(agent): remove CODER_AGENT_IS_SUB_AGENT cli flag (#17875)

The RFC has changed, this information will be passed through the
manifest instead.

agent/agent.go

@@ -89,7 +89,6 @@ type Options struct {
 	ServiceBannerRefreshInterval time.Duration
 	BlockFileTransfer            bool
 	Execer                       agentexec.Execer
-	SubAgent                     bool
 
 	ExperimentalDevcontainersEnabled bool
 	ContainerAPIOptions              []agentcontainers.Option // Enable ExperimentalDevcontainersEnabled for these to be effective.
@@ -191,8 +190,6 @@ func New(options Options) Agent {
 		metrics:            newAgentMetrics(prometheusRegistry),
 		execer:             options.Execer,
 
-		subAgent: options.SubAgent,
-
 		experimentalDevcontainersEnabled: options.ExperimentalDevcontainersEnabled,
 		containerAPIOptions:              options.ContainerAPIOptions,
 	}
@@ -275,8 +272,6 @@ type agent struct {
 	metrics *agentMetrics
 	execer  agentexec.Execer
 
-	subAgent bool
-
 	experimentalDevcontainersEnabled bool
 	containerAPIOptions              []agentcontainers.Option
 	containerAPI                     atomic.Pointer[agentcontainers.API] // Set by apiHandler.

cli/agent.go

@@ -54,7 +54,6 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 		blockFileTransfer   bool
 		agentHeaderCommand  string
 		agentHeader         []string
-		subAgent            bool
 
 		experimentalDevcontainersEnabled bool
 	)
@@ -362,7 +361,6 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 					PrometheusRegistry:               prometheusRegistry,
 					BlockFileTransfer:                blockFileTransfer,
 					Execer:                           execer,
-					SubAgent:                         subAgent,
 					ExperimentalDevcontainersEnabled: experimentalDevcontainersEnabled,
 				})
 
@@ -509,17 +507,6 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 			Description: "Allow the agent to automatically detect running devcontainers.",
 			Value:       serpent.BoolOf(&experimentalDevcontainersEnabled),
 		},
-		{
-			Flag:        "is-sub-agent",
-			Default:     "false",
-			Env:         "CODER_AGENT_IS_SUB_AGENT",
-			Description: "Specify whether this is a sub agent or not.",
-			Value:       serpent.BoolOf(&subAgent),
-			// As `coderd` handles the creation of sub-agents, it does not make
-			// sense for this to be exposed. We do not want people setting an
-			// agent as a sub-agent if it is not.
-			Hidden: true,
-		},
 	}
 
 	return cmd